Temperature compensated inductance



Dec. 9, 1941. J. B. MOORE 2,265,390

TEMPERATURE CQMPENSATED INDUCTANCE Filed Feb. 28, 1939 INVENTOR.

ATTORNEY.

Patented Dec. 9, 1941 TEMPERATURE COMPENSATED INDUCT- ANCE John B. Moore, Riverhead, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application February 28, 1939, Serial No. 259,012

6 Claims.

This invention relates to anew and novel method of controlling-the temperature coefficient of frequency of vacuum tube oscillators, and is particularly adapted to an inductance coil with compensating-means to maintain the oscillator frequency constant-regardless of temperature changes-in the coil 2 An object of this invention is to provide an improved inductance-coil having temperature compensating means.

Another object of this invention is to provide an inductance coil-whichmay be placed in an oscillating circuit =in which the frequency of the oscillator is maintainedsubstantially con stant., I g

Still another object of this invention is to. reduce the temperature coefficient of frequency change of an inductance coil used in vacuum tube oscillators employing conventional circuits, such as the Hartley or Colpitts.

A feature of this invention is the novel arrangement of an adjustable metallic vane within.

the field of the inductance coil, wherein inductance changes due to variation in temperature are compensated by movement of the vane. The frequency of oscillator circuits generally varies with the supply voltage and with the temperature of the component parts. The effects of changes in supply voltage can be minimized by methods well-known in the prior art. Changes in capacitance and inductance of the elements of. the tuned circuit and the tube with changes in the ambient temperaturedepend upon the thermal coeiiicient of the materials used in their construction and in the manner in which these materials are used. Variable tuning condensers are well known in the prior art to have either positive or negative temperature coefficients of capacitance by proper choice and disposition of material used in their construction. However,

in the construction of low loss inductance coils,

coil with the temperature compensating vane located within the center of the coil;

Fig. 2 is a longitudinal section of Fig. 1;

Fig. 3 is an end elevation of another modification of Figs. 1 and 2m which the vane is located at one end of the inductance coil; and

Fig. 4 is a longitudinal section of Fig. 3,

Referring now in detail to Figs. 1 and 2 of the drawing, the coil form I, which is composed of any suitable insulating material having the necessary electrical insulating qualities and mechanical strength, has wound on its outer surface a metallic conductor 2 of low resistivity, the turns of which may be either close wound or suitably spaced. Located within the central portion of the insulating form I is a shaft 3 which carries a flipper plate or vane 4, which is pivoted on shaft 3. The angular position of vane 4 is controlled by a bi-metallic spiral member 5 which is firmly secured at one end to coil form I at point 6 by means of riveting, or any other suitable means, and at the other end to a point I. Movable flipper plate or vane 4 may be of any suitable material. For example, in Fig. 2, the vane is preferably of copper. In Fig. 4, it must necessarily be of spring material.

In the operation of this device, any changes in temperature will vary the angular position of vane 4 within the field of inductance coil 2 and thus provide the proper temperature compensation.

The modifications shown in Figs. 3 and 4 are somewhat similar to that of Figs. 1 and 2, as regards the form I and winding 2; however, the movable vane 4 is located at one end of coil form I and is riveted thereto by means of rivets 8. At the other end of form I, a support member 9 is provided and is secured by means of rivets H), the lower end of support 9 being linked by means of a wire H to coil vane 4.

The operation of this latter modification is generally similar to that of the modification shown in Figs. 1 and 2, except that the link system is composed of two materials having different thermal coefiicients of expansion, and any change in temperature will change the length of wire, and thus change the position of vane 4.

Although only two forms of this modification are shown, it is to be distinctly understood that this invention is not to be limited to the precise arrangement shown.

What is claimed is:

1. An inductance coil having means for compensating for changes in inductance due to temperature variations comprising an insulating support member, a coil winding on the outside of said insulating support member, a movable metallic disc member located at one end of said insulating support member, a wire having a different temperature coefficient of expansion than said insulating support member linked to said movable disc member and secured to the other end of said support whereby changes in temperature varies the position of said movabl memher with respect to the coil winding,

2. An inductance coil having means for compensating for changes in inductance due to temperature variations comprising a hollow insulating support member, a coil winding on the outside said insulating support member, a movable member of spring bronze locatedat one end of said hollow insulating support member, a wire having a diflerent coefiicient oi expansion than said hollow insulating support member, said wire linked to said movable member and secured to the other end of said support member to retain said movable member or spring bronze in tension whereby changes in temperature varies its position with respect to the coil winding.

3. An inductance coil having means for compensating for changes in inductance due to temperature variations comprising a support member, a coil winding on the outside of said support member, a movable member of metal located at said support member, said link member secured to the other end of said support member and coupled to said movable metallic member for moving it with respect to said coil upon changes 7 in temperature.

5. A low loss inductance cell comprising a winding support member, a coil winding on the outside of said support member, a metallic disc member secured by rivets and arranged to be hinged to one end or said support member, a second metallic member of diflerent temperature coeflicient of expansion from that of said windone end of said support member, a wire having a different temperature coeillcient 0! expansion than said support member, said wire linked to said movable member and secured to the other end of said support member whereby changes in temperature varies the position of said movable member with respect to said coil winding.

4. An inductance coil having means for compensating for changes in its inductance-due to temperature variations, a movable metallic member located within the field of said coil, a support member tor-said coil, a winding for said coil,

said movable metallic member secured to one end 7 0! said support member, a metallic link member having a diflerent temperature coefllcient than ing support member and secured to said disc member and riveted to the other end oi. said winding support member opposite from where said disc member is hinged whereby changes in temperature alter the length of said wire and change the position or said disc member with respect to said coil winding.

JOHN B. MOORE. 

